1. Field of the Invention
This invention relates to an apparatus and a method for automatically erasing a blackboard, and more particularly, to an improved apparatus and method for automatically erasing the blackboard wherein the automatic erasing apparatus horizontally reciprocates (or moves back and forth) relative to a blackboard.
2. The Background Art
In general, a stuffed eraser made of fabrics is usually used in order to erase characters written on a conventional blackboard. However, when erasing the blackboard with a stuffed eraser, the user""s respiratory system and/or nasal mucous membranes may be threatened by the chalk dust in the air. The chalk dust also pollutes and dirties the surroundings of the chalkboard.
There is another disadvantage in that the user must physically shake the chalk dust from the eraser after each erasing operation.
There is a further disadvantage in that, since the surface of the blackboard has a prescribed roughness to prevent sliding of the chalk, when the user writes characters on the blackboard with the chalk, chalk particles become embedded in minute concave portions of the surface of the blackboard, so that the fabric eraser cannot completely and clearly erase the characters on the surface of the blackboard, and blurry traces from the erased characters remain on the board.
In order to solve these problems of the prior art, numerous types of automatic erasing apparatuses have previously been proposed. Certain of these known automatic erasing apparatuses are disclosed in Japanese patent publication numbers 8-113000 and 9-193599. Each of these proposed automatic erasing apparatuses is for automatically erasing a blackboard. These automatic erasing apparatuses are operated as follows:
(a) spraying washing liquid on a surface of a blackboard through a first nozzle to dissolve a film layer of chalk attached on the blackboard;
(b) rotating an erasing member such as a brush or a sponge in engagement with the surface of the blackboard to isolate the dissolved chalk from the surface of the blackboard;
(c) again spraying the washing liquid on the surface of the blackboard trough a second nozzle to wash down the dissolved chalk;
(d) temporarily storing the used liquid containing the dissolved chalk in a tank to settle down the fine particles of the chalk;
(e) filtering and pumping up the washing liquid to return it to the tank in order to reuse it;
(f) scrubbing the liquid remaining on the surface of the blackboard with a rubber scrubber in engagement with the blackboard and drying the blackboard with hot air.
The erasing apparatuses illustrated in JP 8-113000 and JP 9-193599 both reciprocate laterally of the elongated blackboard. An eraser member of the erasing apparatus traverses in engagement with the surface of the blackboard during the erasing operation, and traverses in disengagement with the surface of the blackboard when returning to its original position.
However, the previously proposed automatic erasing apparatuses also have several disadvantages which are generally recognized in use. A user must wait until the erasing apparatus finishes one complete operation, i.e., returns to its original position after erasing the blackboard, so it is very inconvenient and is a waste of time.
Moreover, the erasing apparatus in the prior art automatic devices has a decreased lifetime because the erasing apparatus returns to its original position after finishing the erasing operation without being used during its return.
In addition, in the prior art automatic devices, the erasing apparatus cannot erase only a portion of the blackboard (for example, half of the blackboard), because it is fixed to perform the reciprocation relative to the entire blackboard once operation of the erasing apparatus begins.
It is accordingly an object of this invention to provide an improved apparatus and method for automatically erasing a blackboard with an erasing device which overcomes the above disadvantages.
Another object of this invention is to provide an apparatus and a method for automatically erasing a blackboard with an erasing device which reciprocates relative to a blackboard to perform an erasing operation not only while traversing forwardly but also while returning to its original position, thereby providing a cleaner surface of the blackboard.
A further object of this invention is to provide an apparatus and a method for automatically erasing a blackboard with an erasing device which may erase or clean a selected portion of the blackboard as well as the entire surface of the blackboard according to the user""s needs, thereby improving convenience to the user.
The foregoing and other objects and features of the present invention will become more fully apparent to persons of ordinary skill in the art from the following description and appended claims, taken in conjunction with the accompanying drawings.